CA2053223A1 - Vehicle braking systems - Google Patents
Vehicle braking systemsInfo
- Publication number
- CA2053223A1 CA2053223A1 CA 2053223 CA2053223A CA2053223A1 CA 2053223 A1 CA2053223 A1 CA 2053223A1 CA 2053223 CA2053223 CA 2053223 CA 2053223 A CA2053223 A CA 2053223A CA 2053223 A1 CA2053223 A1 CA 2053223A1
- Authority
- CA
- Canada
- Prior art keywords
- braking
- braking element
- override
- piston
- valve
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 230000003213 activating effect Effects 0.000 claims abstract description 7
- 238000001514 detection method Methods 0.000 claims description 3
- 239000012530 fluid Substances 0.000 description 24
- 230000007246 mechanism Effects 0.000 description 10
- 238000006073 displacement reaction Methods 0.000 description 3
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000036316 preload Effects 0.000 description 2
- ZPEZUAAEBBHXBT-WCCKRBBISA-N (2s)-2-amino-3-methylbutanoic acid;2-amino-3-methylbutanoic acid Chemical compound CC(C)C(N)C(O)=O.CC(C)[C@H](N)C(O)=O ZPEZUAAEBBHXBT-WCCKRBBISA-N 0.000 description 1
- SVTBMSDMJJWYQN-UHFFFAOYSA-N 2-methylpentane-2,4-diol Chemical compound CC(O)CC(C)(C)O SVTBMSDMJJWYQN-UHFFFAOYSA-N 0.000 description 1
- 241000726103 Atta Species 0.000 description 1
- 241001052209 Cylinder Species 0.000 description 1
- 101100310856 Drosophila melanogaster spri gene Proteins 0.000 description 1
- 241000490229 Eucephalus Species 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000000994 depressogenic effect Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 230000001050 lubricating effect Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 229920000136 polysorbate Polymers 0.000 description 1
- 101150050071 proY gene Proteins 0.000 description 1
- 108090000623 proteins and genes Proteins 0.000 description 1
- 235000002020 sage Nutrition 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T7/00—Brake-action initiating means
- B60T7/02—Brake-action initiating means for personal initiation
- B60T7/04—Brake-action initiating means for personal initiation foot actuated
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
- B60T13/10—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release
- B60T13/58—Combined or convertible systems
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
- B60T13/10—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release
- B60T13/66—Electrical control in fluid-pressure brake systems
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
- B60T13/74—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with electrical assistance or drive
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T15/00—Construction arrangement, or operation of valves incorporated in power brake systems and not covered by groups B60T11/00 or B60T13/00
- B60T15/02—Application and release valves
- B60T15/04—Driver's valves
- B60T15/14—Driver's valves influencing electric control means
Landscapes
- Engineering & Computer Science (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Braking Systems And Boosters (AREA)
- Regulating Braking Force (AREA)
- Valves And Accessory Devices For Braking Systems (AREA)
Abstract
The invention relates to a vehicle braking system which comprises a braking element (15) operable by a driver, control signal generating means (21) responsive to the operation of the braking element (15), means braking at least one vehicle wheel in response to the generator control signal and also means for activating an override system to enable direct control of the braking means by operation of the braking element, independently of the control signals.
Description
W090/12718 . 20~ 3 2 2 3 PCT/GBgo/00~1 .~ ~ , ... ..
~a~
The invention relates to Yehicle brak~ng syitems.
Almost all modern vehicles, particularly motor cars, have hydraulically operated foot brakes operating on all wheels. The systems generally comprise either dsum or disc brakes with a brake pedal connected to a piston in a master , cylinder whence the hydraulic operating pres~ure originates.
.
Depression of the brake pedal forces the hydraulic brake fluid along a ~etwork of pipes and hoses to wheel cylinders which urge brake calipers or shoes into contact with a brake disc or d~ium to provide the bra~inq action.
H~draulic ~ystems have many a~vantages, such a~ being sel lubricating (reducing the chan~e ~of seizure), hav1n~ a low ~ate~of wesr a~d low ~riction, and enablinq equal pressures to be~.e~erted on all: the brake ~hoes or ~alipers, even compensating for~ . unequal wear or adjustment. Further, install-ation:is .generally. easier. than ro~ mechanical systems be~ause of.the~fle~ibility of the hoses.^~ ............... ~ . ;
3Th~iprincipal disadvantag~ of hydraulic braking systems that';la ~leakage ~n the s~stem or contamlnation of the hjdraulic 1uid u~ed can~render the brakes-ine~fectiee or in-op~rat~ J
. One solution to this problem is proY~ided by h~ing atande~ ~aster cylinder, and splitting ~he sy~tem into two parts ~: :
, .~
WO90~12718 `,` ,~ PCT/GB90/00641 ' : . ", .~, .., :
~a~
The invention relates to Yehicle brak~ng syitems.
Almost all modern vehicles, particularly motor cars, have hydraulically operated foot brakes operating on all wheels. The systems generally comprise either dsum or disc brakes with a brake pedal connected to a piston in a master , cylinder whence the hydraulic operating pres~ure originates.
.
Depression of the brake pedal forces the hydraulic brake fluid along a ~etwork of pipes and hoses to wheel cylinders which urge brake calipers or shoes into contact with a brake disc or d~ium to provide the bra~inq action.
H~draulic ~ystems have many a~vantages, such a~ being sel lubricating (reducing the chan~e ~of seizure), hav1n~ a low ~ate~of wesr a~d low ~riction, and enablinq equal pressures to be~.e~erted on all: the brake ~hoes or ~alipers, even compensating for~ . unequal wear or adjustment. Further, install-ation:is .generally. easier. than ro~ mechanical systems be~ause of.the~fle~ibility of the hoses.^~ ............... ~ . ;
3Th~iprincipal disadvantag~ of hydraulic braking systems that';la ~leakage ~n the s~stem or contamlnation of the hjdraulic 1uid u~ed can~render the brakes-ine~fectiee or in-op~rat~ J
. One solution to this problem is proY~ided by h~ing atande~ ~aster cylinder, and splitting ~he sy~tem into two parts ~: :
, .~
WO90~12718 `,` ,~ PCT/GB90/00641 ' : . ", .~, .., :
2~3223 '~
so that if one part fails the other part can still function.
Obviously, in the event of failure of one part braking efficiency is reduced, and there are situations when this can be dangerous.
Sometimes it would be preferable to control the separate brakes individually for e~ample if one tyre has been worn more than its a~ial counterpart. In standard systems both axial brakes would be operated identically. It would also be useful in brahing systems to be able to control the feel at the braking, as some drivers prefer sharp ~raking and others prefer to have to move the brake pedal some distance before maximum braking is achieved.
''Advances in braking technology have heen restricted because of the problems in-'distribution of:`the'`fluid in the .. . .. ... . . . .
brake'mecha~isms. ' ~ ' 3 According to ths- 'invention there is. provided a , vehicle brakins system comprising a-braking element operable by a~dr1ver '`contro'1S~signal. generating ~lmeans~.responsive to operàtion of the braking element;.~means braking-,at;least,~one v~ëhic'1e'~wheel~in"'response to control:signals :gene,rated by the contro'1 'signal generating means;,~and means for ,activ,ating an override 'sys`tem to:.enable,direct,control o$ ~,the Abraki,ng means by operation :o~the brak1n~ element independently of;.,,~said control signals; .:: a..`::, ",,,~ ",~,,, ,..", , , ..... . ,., , .,. ~ . , . : .. . . : : . .: : .
wo 90"2~18 2 ~ ~ 3 2 2 ~ PCT/GB90/00641 ~" .
The override system can be selectively activated by means of a manual switch, or activated automatically on detection of a system failure on application of a force to the braking element greater than a predetermined force.
Preferably the means for activating said override system comprises a solenoid valve and a power supply thereto, said override system being activated by de-energisation of the solenoid valve.
The solenoîd valve is preferably de-energised on failure in the power supply thereto and/or by a control signal from said control signal generating means.
The override system preferably comprises means for transmitting a force applied to the braking element to operate the braking means.
In a preferred embodiment of the invention the transmitting means comprises a hydraulic piston and cylinder arrangement, the arrangement being such that movement of the piston forces hydraulic fluid in the cylinder to operate the braking means, The braking element preerably moves the piston of said arrangement by hydraulic means or by mechanical means.
: ~ Preferably the mechanical means comprises a moveable rod arranged such that operation of the braking element wîth a force greater than a predetermined force moves said rod which in turn~moves said piston. .
There are preferably provided spring means biassing ~aid rod to provide æaid predetermined orce.
The braking element is preferably~a foot pedal.
A ~preferred embodiment of the ,invention includes means to make the braking means unresponsive to said control slgnals, which means may comprise at least one valve the state of which is changeable by the application of pressure thereto.
' : .. . . - , .. . . .. . . . .. - -WO90/12718 PCr/GB90/00641 ~53~23 4 _ A vehicle braking system according to ~he invention will now be described by way of e~ample with reference to the drawings, in which:-Figure 1 is a schematic representation of the layout of the system: `:
Figure 2 is a part sectional front elevation o a brake~feelr actuator ass~mbly which i a part of the system of Figure l;
Figure 3 is a sectional view o~ Figure 2 o~ III-III;
Figure 4 is a part sectional front elevation o~ a distribution Yalve which is a part of the system of Figure l;
and Figure 5 is a front elevation of the distribution valve ~;of Figure 3 with parts omitted for~clarity. ~ -~:- Réferring first to `Figure 1 there is shown a brakin~
~ ~ , ,,, : . ,, , -system 10 for use in a motor vehicle such as a motor car, . ~ ;,: . ~ , - : : . .
~-having steerabl~ wheel~ (no~ shown). .~
The motor vehicle has ~our wheels`~ ~ach fitted with : standard hydraulically operated disc or drum bra~es. Although , . ., , ., ,," ~ ',, . " '`, ' '`,! . . . ' , ' ~, .. , . ~, " , ' the jb~akes~ themselYes ,are not æhown in the drawings, the : operable calipérs br shoes: or~each wheel (hereina~ter brake : iméchan?~m) are atta~hed to a respective servo ~alve 11, 12, 13, :
: :
' .
WO90/12718 2 ~ 5 3 2 2 3 PCT/~Bgo/00641 ~- 5 -. I ....
14, which independently controls the pressure to the brake mechanism at the associated wheel.
The system 10 combines a primary active brake system and a secondary brakè override system that provides the braking effort in the e~ent of a system failure or when the active system is turned off.
The Primary_~iye Brakina S~stem The active system is a fully active ~feel~ system including a braking element in the form of a brake pedal 15 which is physically decoupled from the braking mechanisms. The brake pedal 15 is mounted to the vehicle body to be pivotal about its point of attachment. Attached to the brake pedal 15 is a ~feel~ actuator 16.
Referring now to Figure 2 also, the feel actuator 16 is a double acting hydrauIic actuator comprising a moveable piston 17 having a pair of opposed piston faces and contained in a cylinder 18. ~ounted on the piston 17 is a piston head 17a which provides the pis~on`~aces. One end of the piston 17 is coupled to the brake pedal 15 by means of a linkage`element 20 whi~h includes a load cèll 21 ~or other suitable de~ice) which r~
is preferably a duplez sensor, for sensing the orce applied by a driver of ~he vehiclé` to the brake pedal lS~ The load cell .~ , , ., .~1,. , , , " , , ~ , . . . .. . . ...
21 iS elec~rically connected to a control unit 25, such as a mircoproc~ssor, and sends inpùt signàls thereto relating to the force applied to ~he brake pedal 15.
Also attached to the linkage element 20 is a ro~ 22 ..
:
:' ' . . . ~, , ., : . , :
WOg~tl2718 . PCT/GB90/00641 - 6 - ( 2~3223 which enters a holder 23 of a linear variable differential transformer (LVDT) 24. The ~VDT holder 23 is fi~ed adjacent to the cylinder 18 on a manifold block 7~ housing the feel actuator 16. The LVDT 24 ~onverts the mechanical displacement of the linkage element 20 (and therefore the displacement of the brake pedal 15) into an electrical signal which is transmitted to the microprocessor 25 to which the LVDT 24 is electrically connected. Other sultable deYices may of course ~e used for converting the displacement into an el ctrical siynal.
The feel actuator 16 is hydraulically connected to ~ervo valve 28. Hydraulic transfer tubes 9 are provided in th~
manifold block 75 linking the hydraulic fluid lines from the servo ~alve 28 to each end of cylinder 18 so that the servo valve 28 may be used ~o control the movement of the piston 17 by hydraulic pressure to either side of ~he piston head 17a.
; As will be seen in Figure 1 a non-return valve 29a is included in the hydraulic fluid l~ne between the servo ~alve 28 and feel actuator 16, for reasons described below. The non-return valYe 29a is also connected .to the pressure supply line,.33.via an isol~ting ~alve 31 described below. The non-return valve 29a opens on application o pressure thereto.
The servo valve 28 is connected to hydraulic fluidsupp~ly pressure ~ and return lines 33, 34 Yia an isolating valve 31 ~which is preferably a solenoid valve. When the solenoid valve.31 is energised the pressure supply line 33 is connected :
: :
WO90/12718 2 ~ ~ 3 2 2 3 PCT/GB90/00641 _ 7 _ . ' '' ` ' '.;
to the servo valve 28 and when it is de-energised the return line 34 is connected to the servo valve 28. A pressure reducing valve 30 is incorporated in the pressure supyly line 33 leadi~g to the isolating valve 31 so that the servo valve 28 uses a pressure lower than the system pressure.
An anti-cavitation valve 27 is also included.
The microprocessor 25 is connected to control the brake servo valves 11, 12, 13, 14 and signals generated by the micro-processor 25 control the pressure applied to the four brake mechanisms indepPndently. The servo valves 11, 12, 13, 14 are connected to brake lines 56 which are connected to the brake mechanisms of the front left, rear left, rear right and front brakes respective7y, via a distribution valve 35, as shown in Figures 4 and 5.
The servo valves ll, 12, 13, 14 are connected to the : hydraulic pres~ure and return lines 33, 34 via connectors 32.
One connector`'32 ~co~nects :a branch of the pressure and return nes to one ~pair of ~servo valves 11, l~ and the other c~nnéctor 32 to the second pair of servo valves:l2, 13.
The Difi~ri~iQn Valve ;
!The` distribùtion valve 35 comprises a valve manifold 35 -' i- having ~our s`èparate chambers 46, 47,.48, 49 therein. Each-chamber';-46, i7, 48, 49 is connected via a ~luid pa~sage S0 to a .respe~tive~servo valve 11,` 12,::13,:14. The manifold 36 has -éig~t po~ts 37-'44 therein suchithat each chamber 46, 47,l48, 4g i has a'pair of ports ~37,-'41), ~38, 42), ~39, 43), ~40, 44) ~ :
, : . : : .
WO90/1~7~ PCT/GB90/~0641 . - B -2 ~ 2 ~
therein. One port 37, 38, 39, 4d of each pair is hydraulicallyconnected to a master cylinder 45 Yia a pair of 1uid lines 58, 59. The master cylinder 45 is preferably a tandem master cylinder and has a hydraulic booster 45a attached thereto, the function of which will be e~plained latPr.
As shown in Figur~ 1, one pair of ports 37, 38 feeds from one fluid line 58 from the master cylinder whilst the second pair of ports 3g, 40 feeds from the second fluid line 59. A balancing valve 60 may be proYided in one of the fluid lines 58, 59~ . .
The-other ports 41, 42, 43, 44 are connected to a brake li~e 56 leading to a brake ~echanism.
. Within each chamber 46, 47, 48, 49 is a spool 51 comprising a concave first part 52 which is lecated in one end of a concave second part 53, the two parts 52 and 53 being secured together by a screw 55. As shown the two parts 52 and 53 ~are of different materials in ~iew of the.possibly different 1uids acting on the two parts. The spool 51 is slida~le - , .
~ ~within the chamber 46`, 47, 48, 49. -, : ~ ~ A~compression spri~g 54 is also located in each .chamber ~, J..~46, 47,^ 4B,t 4g,.with one end located against an~inside ace 55 o the~second spool.part.53 ~o aæ to bias the spool.51 outwards . to..lseal.;~off.:the fluid passage 50 between the chamber 46, 47, 48,~m.49 .;a~d the as~ociated servo ~alv~ 11,, 12, 13, .14. The length-o~ -th~ spool 51. is such that when it .is ,biased as mentioned above brake 1uid from the master cylind~r 45 is free '.
:'. ' ` ' , ~ . ` : , , ~ . , ` ' ' ~ ' ' ' . '`,' ~ ' '' '.' . ' ~ ,,.' ,''' ' WO90/12i718 ~ 3 PCT/GB9 to enter/leave the chambers 46, 47, 48, 49 via the ports 37-44.
When hydraulic pressure is ap~lied via pressure line 33 to the end face 57 of the spool part 53 the bias of the spring 54 is overcome and the spool 51 moves to compress the spring 54 and seals off the chambers 46, 47, 48, 49 from the ports 37-40.
S~cond~ry ~r~kinq Sy~t~
A secondary braking system is also~ incorporated, the secondary system being isolated when the primary active system is operating and thus providin~ no braking effort. However, when the primary ~acti~e system is turned off or fails the secondary system is selectively activated, for esample by a positive decision from the driver who operates a manual switch, or by automatic decision from the system in the event of a failure.
The second system utilises a secondary hydraulic actuator 65 to operate the booster 45a which in turn operates the master cylinder 45 in a known manner to supply pressurised fluid to f1uid lines S3, 59.
:
The àctuator: 65 comprises a piston 66 having a single head 6i within'a cylinder ~8. The sècondary actuator 65 is ~ hydraulicaily linked to the ^eel actuator 16 as ollows.
'' hydrauilic flùid line 69 isiconnected to the crlinder fiB on onè
j side of the pi~ton head`67. Ater the 1uid line 69 leaves the , , ,,, ,,~ ", , , . ,. , , , , ; , , . cylinder G8 it divides into two, one branch 69a connecting to the`'hydraulic`'fluid return'iine'34 via a~non-return-~val~e 29b, and the~'second brànch 69b leading to a switching valve 70. The . ~:
: :
;~ ~
-. .. ~, ... .
2Q~3223 switching valve 70 has a fluid line 71 which splits into two branches 71a, 71b; branch 71a leads to the non-return valve 29a and branch 71b to the cylinder 18 of the feel actuator 16.
The non-return valYes 29a, 29b and the switching valve 7~ are connected to. the pressure supply line ~3 via the isolating valve 31.
T~ M~ani~ 1 Qv~;ide In the event of an undetected failure in the primary active braking. system an override mechanism comes into automatic operation. Vnder normal braking conditions the brake pedal 1~ may be depressed over distance A shown in Fi~ure 2.
When ,the braking pedal 15 is subjected to a ~panic~ force in the event of a failure undetected b~ the system 10 so that no braking occurs during the normal travel A of the pedal 15, the .: pedal 15.,moves through distance B .and operates the override ,,~ mechanismt~
,,, .. The override mechanism comprises a shaft.76 mounted on the piston 66 of the actuator 65 and located within a cylinder . ~..,.77, e~tending between:~the ?ctuators 1~ and 65. Under normal conditions the shat 76 does not.contact the cylinder 77.
, 7 ~ ^ An override~compression ~spring 74,is located,be,tween the ,"~ manifold: block~75!,which"~houses. the ,actuator 16~ and,,,,a, fi~ed .,',.'4 ', support 78 on ~hich the cylinder 7,7.1s mounted on a,piYotal arm ., ,~J9;.,see Figures~ and,3.~j,The.manifolld block 75 ls,mounted in the,-1system;;l0 .~to ,be moveable~ ut ls. held, ? during,,. !normal .~: braking,; skationar~,by khe spring ;74 acting between the block 75 . .
., , . - . .
.. ~ . ~ . . . :
, ~ . . .- . ~ . ....
WO9Otl2718 ~ 3 2 2 3 PCT/~90/00641 . ................. , - 1~
. .
and the support 78.
Figure, ~ shows the system in the condition when the override is operating, although the pedal 15 is shown in solid line in its normal position.
PrimarY A~tive B~akinq Durin~ primary active braking brake pedal 15 travels through distance A (see Figure 2). The load applied by the driver to the pedal 15 is measurPd by load cell 21 which sends input sig~als relating to the load to the microprocessor 25.
A reaction to tha driver's demand on the brake pedal 15 is provided by the feel actuator 16. To do this the miCroproc2ssor 25 sends control signals to the servo valve 28 which is connected to the feel actuator 16 to apply pressure to either side of the piston head 17a. This is used to provide resistance to movement of the brake pedal 15 and to generally simulate the "feel~ o braking. This ~feel~ may be altered by programming the microprocessor;25 to provide li~ht or heavy braking or whatever the driver prefers.
: During primary active;braking the .isolating valve 31 is energised to connec~ the servo ~alve 28 with the pressure line 33.~'JWhen-~the isolating valve 31 is energised pressure is also applied'to...the anon-return ,valves '! 29a,~29b.. This causes the non-return valves 29a, 29b to open and the switching ~alve 70 to close whiCh allows the eel actuator 16 to.~b0 driven directly ~by~the:.servo ~alve 28 -via the fluld .lines to either side~of the ~piston head .17a. ,.iAny residual ;fluid pressure in :
".
WO90il2718 PCT/GB90/00641 ~53'~`3" 12 - (' the master cylinder 45 is vented ~ia fluid line 69 through the open non-return valve 29b to the fluid return line 34.
The feel actuator 16 is capable of simulating a wide range of characteristics depending on the 'feel' required.
The actual braking is carried out by fluid pressure supplied by the four servo valves ll, 12~ l3, 14. The microprocessor 25 sends independent control signals to each of the servo valves 11, 12, 13, 14, according to input si~nals from the load cell 21. .
Since the isolating valve 31 is energised the servo Yal~es ll~ 12, 130 14 are connected to the pressure supply line ~ia the connectors 32. ; The fluid pressure is controlled by each serYo valve ll, 12, 13, 14 to operate each brake mechanism independently. The fluid pressure transmitted ~rom the servo valves ll, l~, 13, 14 ~ia fluid passages 50 is sufficient to ; overcome the preload on the springs:54 causing the spools S} to move in the chambers 46~ 47, 48, 49 to seal them off from the ports 37--40 from :the master:cylinder 45. The fluid remaining in -the chambers-~6-49 is forced ;out-of the chambers 46-49 via ,~ ~" ?~he ports `41-44'by mo~ement'~of the spools 51 to the individual bra~ë?~mechanisms~ to operate the brakes independe~tly of each `' other', ' w~ '.";t~
i - J J J Thë secondary ~braking- system may .be activated .in two ?ways`,~ithër~y means~o f'7a manual swit~h tnot shown) operated ' ' .
WO90/127l8 ~ 3 2 2 3 PCT/GB90/00641 by the driver to de-energise the isolating valve 31, or as a result of a ailure detected in the primary active braking system .
The main failures may be in the form of loss of electrical power to 'che system of a drop in the systern pressure below a pre-set safety limit.
Yarious safety control loops may be incorporated in the overall braking system which are monitored by the mirroproce~sor 25. An e~ample described earlier in the provision of the LVDT 24 which checks whether the eel actuator 16 is in fac~ operating according to the control si~nals sen~
to the servo valve 28 by the microproce~sor 25. The LYDT, load cell 21 and other sensors in the system are pre~erably duple2 sensors. Their signals are duplicated and the signals combined to give a de~and and an error detection signal. Failures in the control loops 'can be detected by comparing the:actual output from the system with a real time.imodel of the system running in parallel.~ Any detected failures wi}l result in de-energisation o~ the isolating valve 31.. ~ -.
Loss o~ the ~lectrical ~upply!will automatically result in de-engerisation ofithe:isolating.val~e 31. The effect of J~'~ los's '0~ ;pressurelhas a `similar effectJwhich will be described later~ ; : ' ~ ~ / -'~ - ' When the isolating valve 31 is:de-energised;it connects to- the ~fluid return~;line 34. This results ~:in.~ a drop in `pressùre to th~ non-retur~n valv~ 29a, 29b which close and the WO90/12718 . ~ PCT/GB90/00641 -- 1 ~ -- ......
?.Q~322~
and switching valve 70 which opens. This hydraulically disconnects the servo valve 28 from the feel actuator 16 and hydraulically connects the feel actuator 16 to the secondary hydraulic actuator 65 via switching valve 70 which operates the booster 45a and master cylinder 45.
Thus pressure applied to the pedal 15 will be transmitted by mo~ement of the piston 17 with piston head 17a forcing the fluid out of cylinder 18, via the switching valve 70, into the cylinder 68 of the secondary actuator 68 to act on the piston head 66 of the secondary actuator 68. Thus, braking in ~his mode ~feels and performs similar to a standard unmodified hydraulic braking sy~tem.
Referring to the distribution valve 35, in secondary br3king the servo valves 11-14 are connected to the 1uid return line 34 and the pressure applied to the spools Sl drops. The force of springs 54 is sufficient to overcome any residual pressure and force the spools Sl outwards towards the : servo valves ll-l~ to 6eal~ offi fluid. passages 50 from the : ~ chambers 46-4g and:-~he ports 37 40 which communicate with the ~master cylinder 45 are.uncovered.
'~ Thus,.as thè:~foot.pedal lS is depre~sed brake 1u.id is :forcedtalong the~::fluid:linas S8, 59 ~rom the master c~linder 45, into chamb~rs 46-49 and out o ports 41-44 to ~he brake .mechanism via:the brake line~ 56. ..~
, Since ports 37, ~0 are conneoted~to the fluid line 58 ~and ports 38, 39 are.connected to line ~9 equal pressures are :
, :. . , , . ~ . ~, .,: . . :. ~ . .: . . .
WO90~12718 2 ~ ~ 3 % % 3 PCT/GBgo/00641 . . 1 transferred across each a~le pair of brakes, Loss of system pressure below a certai.n limit will also allow the springs 54 to recover and return to their original state a~d thus has the same effect as if the isolating valve 31 had been de-energised.
Ov~rrid~ Brakinq In the e~ent o~ an undetected failure in the feel system the override mechanism comes into operation. If ~o braking occurs when the dri~er depresses pedal 15 through distance A, he will use a panic force and the pedal will mo~e through distance B. The length of the feel actuator cylinder 18 is such that ~hen the brake pedal 15 has reached the end of travel distance A, the piston head 17a reaches the end of the cylinder 18. Further movement of the pedal 15, i.e. through travel d1stance B on applicaton of a panic force, will cause the piston head 17a to bear on the end face 80 of the cylinder 18, which is attached to the manifold b}ock 75 and thus causes the manifo:ld block 75 to move against and overcome the pre-load o~
riDg 74 so that the whole manifold block 75 mo~es (~o the : positio~ shown as Figure 2). As the maniold block 75 moves toward the support 7~ cylinder 77 mo~es into contact with shaft 76. Further movement of the block 75 caused the shaft 76 to move the piston 66, which acti~ates the brake booster ~Sa and master cyl inder 45 to operate the brakes. ~:
The system is tbus~ery vers tile, self-monitoring, fail-sae and may pertorm to a variety of control laws, such as anti-.
. .
WO 90/12718 ` ~ . ~; PC~/GB90/00643 2~ 33223 lock nraking, variable Dalance, deceleration demand and brakeperformance feed back to pedal.
Although the system described above operates primari ly in dependence upon the load applied to the brake pedal, with appropriate modifications to the system it may be made responsive to the position or movement of the brake pedal or any other parameter measurable in the system.
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so that if one part fails the other part can still function.
Obviously, in the event of failure of one part braking efficiency is reduced, and there are situations when this can be dangerous.
Sometimes it would be preferable to control the separate brakes individually for e~ample if one tyre has been worn more than its a~ial counterpart. In standard systems both axial brakes would be operated identically. It would also be useful in brahing systems to be able to control the feel at the braking, as some drivers prefer sharp ~raking and others prefer to have to move the brake pedal some distance before maximum braking is achieved.
''Advances in braking technology have heen restricted because of the problems in-'distribution of:`the'`fluid in the .. . .. ... . . . .
brake'mecha~isms. ' ~ ' 3 According to ths- 'invention there is. provided a , vehicle brakins system comprising a-braking element operable by a~dr1ver '`contro'1S~signal. generating ~lmeans~.responsive to operàtion of the braking element;.~means braking-,at;least,~one v~ëhic'1e'~wheel~in"'response to control:signals :gene,rated by the contro'1 'signal generating means;,~and means for ,activ,ating an override 'sys`tem to:.enable,direct,control o$ ~,the Abraki,ng means by operation :o~the brak1n~ element independently of;.,,~said control signals; .:: a..`::, ",,,~ ",~,,, ,..", , , ..... . ,., , .,. ~ . , . : .. . . : : . .: : .
wo 90"2~18 2 ~ ~ 3 2 2 ~ PCT/GB90/00641 ~" .
The override system can be selectively activated by means of a manual switch, or activated automatically on detection of a system failure on application of a force to the braking element greater than a predetermined force.
Preferably the means for activating said override system comprises a solenoid valve and a power supply thereto, said override system being activated by de-energisation of the solenoid valve.
The solenoîd valve is preferably de-energised on failure in the power supply thereto and/or by a control signal from said control signal generating means.
The override system preferably comprises means for transmitting a force applied to the braking element to operate the braking means.
In a preferred embodiment of the invention the transmitting means comprises a hydraulic piston and cylinder arrangement, the arrangement being such that movement of the piston forces hydraulic fluid in the cylinder to operate the braking means, The braking element preerably moves the piston of said arrangement by hydraulic means or by mechanical means.
: ~ Preferably the mechanical means comprises a moveable rod arranged such that operation of the braking element wîth a force greater than a predetermined force moves said rod which in turn~moves said piston. .
There are preferably provided spring means biassing ~aid rod to provide æaid predetermined orce.
The braking element is preferably~a foot pedal.
A ~preferred embodiment of the ,invention includes means to make the braking means unresponsive to said control slgnals, which means may comprise at least one valve the state of which is changeable by the application of pressure thereto.
' : .. . . - , .. . . .. . . . .. - -WO90/12718 PCr/GB90/00641 ~53~23 4 _ A vehicle braking system according to ~he invention will now be described by way of e~ample with reference to the drawings, in which:-Figure 1 is a schematic representation of the layout of the system: `:
Figure 2 is a part sectional front elevation o a brake~feelr actuator ass~mbly which i a part of the system of Figure l;
Figure 3 is a sectional view o~ Figure 2 o~ III-III;
Figure 4 is a part sectional front elevation o~ a distribution Yalve which is a part of the system of Figure l;
and Figure 5 is a front elevation of the distribution valve ~;of Figure 3 with parts omitted for~clarity. ~ -~:- Réferring first to `Figure 1 there is shown a brakin~
~ ~ , ,,, : . ,, , -system 10 for use in a motor vehicle such as a motor car, . ~ ;,: . ~ , - : : . .
~-having steerabl~ wheel~ (no~ shown). .~
The motor vehicle has ~our wheels`~ ~ach fitted with : standard hydraulically operated disc or drum bra~es. Although , . ., , ., ,," ~ ',, . " '`, ' '`,! . . . ' , ' ~, .. , . ~, " , ' the jb~akes~ themselYes ,are not æhown in the drawings, the : operable calipérs br shoes: or~each wheel (hereina~ter brake : iméchan?~m) are atta~hed to a respective servo ~alve 11, 12, 13, :
: :
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WO90/12718 2 ~ 5 3 2 2 3 PCT/~Bgo/00641 ~- 5 -. I ....
14, which independently controls the pressure to the brake mechanism at the associated wheel.
The system 10 combines a primary active brake system and a secondary brakè override system that provides the braking effort in the e~ent of a system failure or when the active system is turned off.
The Primary_~iye Brakina S~stem The active system is a fully active ~feel~ system including a braking element in the form of a brake pedal 15 which is physically decoupled from the braking mechanisms. The brake pedal 15 is mounted to the vehicle body to be pivotal about its point of attachment. Attached to the brake pedal 15 is a ~feel~ actuator 16.
Referring now to Figure 2 also, the feel actuator 16 is a double acting hydrauIic actuator comprising a moveable piston 17 having a pair of opposed piston faces and contained in a cylinder 18. ~ounted on the piston 17 is a piston head 17a which provides the pis~on`~aces. One end of the piston 17 is coupled to the brake pedal 15 by means of a linkage`element 20 whi~h includes a load cèll 21 ~or other suitable de~ice) which r~
is preferably a duplez sensor, for sensing the orce applied by a driver of ~he vehiclé` to the brake pedal lS~ The load cell .~ , , ., .~1,. , , , " , , ~ , . . . .. . . ...
21 iS elec~rically connected to a control unit 25, such as a mircoproc~ssor, and sends inpùt signàls thereto relating to the force applied to ~he brake pedal 15.
Also attached to the linkage element 20 is a ro~ 22 ..
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WOg~tl2718 . PCT/GB90/00641 - 6 - ( 2~3223 which enters a holder 23 of a linear variable differential transformer (LVDT) 24. The ~VDT holder 23 is fi~ed adjacent to the cylinder 18 on a manifold block 7~ housing the feel actuator 16. The LVDT 24 ~onverts the mechanical displacement of the linkage element 20 (and therefore the displacement of the brake pedal 15) into an electrical signal which is transmitted to the microprocessor 25 to which the LVDT 24 is electrically connected. Other sultable deYices may of course ~e used for converting the displacement into an el ctrical siynal.
The feel actuator 16 is hydraulically connected to ~ervo valve 28. Hydraulic transfer tubes 9 are provided in th~
manifold block 75 linking the hydraulic fluid lines from the servo ~alve 28 to each end of cylinder 18 so that the servo valve 28 may be used ~o control the movement of the piston 17 by hydraulic pressure to either side of ~he piston head 17a.
; As will be seen in Figure 1 a non-return valve 29a is included in the hydraulic fluid l~ne between the servo ~alve 28 and feel actuator 16, for reasons described below. The non-return valYe 29a is also connected .to the pressure supply line,.33.via an isol~ting ~alve 31 described below. The non-return valve 29a opens on application o pressure thereto.
The servo valve 28 is connected to hydraulic fluidsupp~ly pressure ~ and return lines 33, 34 Yia an isolating valve 31 ~which is preferably a solenoid valve. When the solenoid valve.31 is energised the pressure supply line 33 is connected :
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WO90/12718 2 ~ ~ 3 2 2 3 PCT/GB90/00641 _ 7 _ . ' '' ` ' '.;
to the servo valve 28 and when it is de-energised the return line 34 is connected to the servo valve 28. A pressure reducing valve 30 is incorporated in the pressure supyly line 33 leadi~g to the isolating valve 31 so that the servo valve 28 uses a pressure lower than the system pressure.
An anti-cavitation valve 27 is also included.
The microprocessor 25 is connected to control the brake servo valves 11, 12, 13, 14 and signals generated by the micro-processor 25 control the pressure applied to the four brake mechanisms indepPndently. The servo valves 11, 12, 13, 14 are connected to brake lines 56 which are connected to the brake mechanisms of the front left, rear left, rear right and front brakes respective7y, via a distribution valve 35, as shown in Figures 4 and 5.
The servo valves ll, 12, 13, 14 are connected to the : hydraulic pres~ure and return lines 33, 34 via connectors 32.
One connector`'32 ~co~nects :a branch of the pressure and return nes to one ~pair of ~servo valves 11, l~ and the other c~nnéctor 32 to the second pair of servo valves:l2, 13.
The Difi~ri~iQn Valve ;
!The` distribùtion valve 35 comprises a valve manifold 35 -' i- having ~our s`èparate chambers 46, 47,.48, 49 therein. Each-chamber';-46, i7, 48, 49 is connected via a ~luid pa~sage S0 to a .respe~tive~servo valve 11,` 12,::13,:14. The manifold 36 has -éig~t po~ts 37-'44 therein suchithat each chamber 46, 47,l48, 4g i has a'pair of ports ~37,-'41), ~38, 42), ~39, 43), ~40, 44) ~ :
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WO90/1~7~ PCT/GB90/~0641 . - B -2 ~ 2 ~
therein. One port 37, 38, 39, 4d of each pair is hydraulicallyconnected to a master cylinder 45 Yia a pair of 1uid lines 58, 59. The master cylinder 45 is preferably a tandem master cylinder and has a hydraulic booster 45a attached thereto, the function of which will be e~plained latPr.
As shown in Figur~ 1, one pair of ports 37, 38 feeds from one fluid line 58 from the master cylinder whilst the second pair of ports 3g, 40 feeds from the second fluid line 59. A balancing valve 60 may be proYided in one of the fluid lines 58, 59~ . .
The-other ports 41, 42, 43, 44 are connected to a brake li~e 56 leading to a brake ~echanism.
. Within each chamber 46, 47, 48, 49 is a spool 51 comprising a concave first part 52 which is lecated in one end of a concave second part 53, the two parts 52 and 53 being secured together by a screw 55. As shown the two parts 52 and 53 ~are of different materials in ~iew of the.possibly different 1uids acting on the two parts. The spool 51 is slida~le - , .
~ ~within the chamber 46`, 47, 48, 49. -, : ~ ~ A~compression spri~g 54 is also located in each .chamber ~, J..~46, 47,^ 4B,t 4g,.with one end located against an~inside ace 55 o the~second spool.part.53 ~o aæ to bias the spool.51 outwards . to..lseal.;~off.:the fluid passage 50 between the chamber 46, 47, 48,~m.49 .;a~d the as~ociated servo ~alv~ 11,, 12, 13, .14. The length-o~ -th~ spool 51. is such that when it .is ,biased as mentioned above brake 1uid from the master cylind~r 45 is free '.
:'. ' ` ' , ~ . ` : , , ~ . , ` ' ' ~ ' ' ' . '`,' ~ ' '' '.' . ' ~ ,,.' ,''' ' WO90/12i718 ~ 3 PCT/GB9 to enter/leave the chambers 46, 47, 48, 49 via the ports 37-44.
When hydraulic pressure is ap~lied via pressure line 33 to the end face 57 of the spool part 53 the bias of the spring 54 is overcome and the spool 51 moves to compress the spring 54 and seals off the chambers 46, 47, 48, 49 from the ports 37-40.
S~cond~ry ~r~kinq Sy~t~
A secondary braking system is also~ incorporated, the secondary system being isolated when the primary active system is operating and thus providin~ no braking effort. However, when the primary ~acti~e system is turned off or fails the secondary system is selectively activated, for esample by a positive decision from the driver who operates a manual switch, or by automatic decision from the system in the event of a failure.
The second system utilises a secondary hydraulic actuator 65 to operate the booster 45a which in turn operates the master cylinder 45 in a known manner to supply pressurised fluid to f1uid lines S3, 59.
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The àctuator: 65 comprises a piston 66 having a single head 6i within'a cylinder ~8. The sècondary actuator 65 is ~ hydraulicaily linked to the ^eel actuator 16 as ollows.
'' hydrauilic flùid line 69 isiconnected to the crlinder fiB on onè
j side of the pi~ton head`67. Ater the 1uid line 69 leaves the , , ,,, ,,~ ", , , . ,. , , , , ; , , . cylinder G8 it divides into two, one branch 69a connecting to the`'hydraulic`'fluid return'iine'34 via a~non-return-~val~e 29b, and the~'second brànch 69b leading to a switching valve 70. The . ~:
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2Q~3223 switching valve 70 has a fluid line 71 which splits into two branches 71a, 71b; branch 71a leads to the non-return valve 29a and branch 71b to the cylinder 18 of the feel actuator 16.
The non-return valYes 29a, 29b and the switching valve 7~ are connected to. the pressure supply line ~3 via the isolating valve 31.
T~ M~ani~ 1 Qv~;ide In the event of an undetected failure in the primary active braking. system an override mechanism comes into automatic operation. Vnder normal braking conditions the brake pedal 1~ may be depressed over distance A shown in Fi~ure 2.
When ,the braking pedal 15 is subjected to a ~panic~ force in the event of a failure undetected b~ the system 10 so that no braking occurs during the normal travel A of the pedal 15, the .: pedal 15.,moves through distance B .and operates the override ,,~ mechanismt~
,,, .. The override mechanism comprises a shaft.76 mounted on the piston 66 of the actuator 65 and located within a cylinder . ~..,.77, e~tending between:~the ?ctuators 1~ and 65. Under normal conditions the shat 76 does not.contact the cylinder 77.
, 7 ~ ^ An override~compression ~spring 74,is located,be,tween the ,"~ manifold: block~75!,which"~houses. the ,actuator 16~ and,,,,a, fi~ed .,',.'4 ', support 78 on ~hich the cylinder 7,7.1s mounted on a,piYotal arm ., ,~J9;.,see Figures~ and,3.~j,The.manifolld block 75 ls,mounted in the,-1system;;l0 .~to ,be moveable~ ut ls. held, ? during,,. !normal .~: braking,; skationar~,by khe spring ;74 acting between the block 75 . .
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WO9Otl2718 ~ 3 2 2 3 PCT/~90/00641 . ................. , - 1~
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and the support 78.
Figure, ~ shows the system in the condition when the override is operating, although the pedal 15 is shown in solid line in its normal position.
PrimarY A~tive B~akinq Durin~ primary active braking brake pedal 15 travels through distance A (see Figure 2). The load applied by the driver to the pedal 15 is measurPd by load cell 21 which sends input sig~als relating to the load to the microprocessor 25.
A reaction to tha driver's demand on the brake pedal 15 is provided by the feel actuator 16. To do this the miCroproc2ssor 25 sends control signals to the servo valve 28 which is connected to the feel actuator 16 to apply pressure to either side of the piston head 17a. This is used to provide resistance to movement of the brake pedal 15 and to generally simulate the "feel~ o braking. This ~feel~ may be altered by programming the microprocessor;25 to provide li~ht or heavy braking or whatever the driver prefers.
: During primary active;braking the .isolating valve 31 is energised to connec~ the servo ~alve 28 with the pressure line 33.~'JWhen-~the isolating valve 31 is energised pressure is also applied'to...the anon-return ,valves '! 29a,~29b.. This causes the non-return valves 29a, 29b to open and the switching ~alve 70 to close whiCh allows the eel actuator 16 to.~b0 driven directly ~by~the:.servo ~alve 28 -via the fluld .lines to either side~of the ~piston head .17a. ,.iAny residual ;fluid pressure in :
".
WO90il2718 PCT/GB90/00641 ~53'~`3" 12 - (' the master cylinder 45 is vented ~ia fluid line 69 through the open non-return valve 29b to the fluid return line 34.
The feel actuator 16 is capable of simulating a wide range of characteristics depending on the 'feel' required.
The actual braking is carried out by fluid pressure supplied by the four servo valves ll, 12~ l3, 14. The microprocessor 25 sends independent control signals to each of the servo valves 11, 12, 13, 14, according to input si~nals from the load cell 21. .
Since the isolating valve 31 is energised the servo Yal~es ll~ 12, 130 14 are connected to the pressure supply line ~ia the connectors 32. ; The fluid pressure is controlled by each serYo valve ll, 12, 13, 14 to operate each brake mechanism independently. The fluid pressure transmitted ~rom the servo valves ll, l~, 13, 14 ~ia fluid passages 50 is sufficient to ; overcome the preload on the springs:54 causing the spools S} to move in the chambers 46~ 47, 48, 49 to seal them off from the ports 37--40 from :the master:cylinder 45. The fluid remaining in -the chambers-~6-49 is forced ;out-of the chambers 46-49 via ,~ ~" ?~he ports `41-44'by mo~ement'~of the spools 51 to the individual bra~ë?~mechanisms~ to operate the brakes independe~tly of each `' other', ' w~ '.";t~
i - J J J Thë secondary ~braking- system may .be activated .in two ?ways`,~ithër~y means~o f'7a manual swit~h tnot shown) operated ' ' .
WO90/127l8 ~ 3 2 2 3 PCT/GB90/00641 by the driver to de-energise the isolating valve 31, or as a result of a ailure detected in the primary active braking system .
The main failures may be in the form of loss of electrical power to 'che system of a drop in the systern pressure below a pre-set safety limit.
Yarious safety control loops may be incorporated in the overall braking system which are monitored by the mirroproce~sor 25. An e~ample described earlier in the provision of the LVDT 24 which checks whether the eel actuator 16 is in fac~ operating according to the control si~nals sen~
to the servo valve 28 by the microproce~sor 25. The LYDT, load cell 21 and other sensors in the system are pre~erably duple2 sensors. Their signals are duplicated and the signals combined to give a de~and and an error detection signal. Failures in the control loops 'can be detected by comparing the:actual output from the system with a real time.imodel of the system running in parallel.~ Any detected failures wi}l result in de-energisation o~ the isolating valve 31.. ~ -.
Loss o~ the ~lectrical ~upply!will automatically result in de-engerisation ofithe:isolating.val~e 31. The effect of J~'~ los's '0~ ;pressurelhas a `similar effectJwhich will be described later~ ; : ' ~ ~ / -'~ - ' When the isolating valve 31 is:de-energised;it connects to- the ~fluid return~;line 34. This results ~:in.~ a drop in `pressùre to th~ non-retur~n valv~ 29a, 29b which close and the WO90/12718 . ~ PCT/GB90/00641 -- 1 ~ -- ......
?.Q~322~
and switching valve 70 which opens. This hydraulically disconnects the servo valve 28 from the feel actuator 16 and hydraulically connects the feel actuator 16 to the secondary hydraulic actuator 65 via switching valve 70 which operates the booster 45a and master cylinder 45.
Thus pressure applied to the pedal 15 will be transmitted by mo~ement of the piston 17 with piston head 17a forcing the fluid out of cylinder 18, via the switching valve 70, into the cylinder 68 of the secondary actuator 68 to act on the piston head 66 of the secondary actuator 68. Thus, braking in ~his mode ~feels and performs similar to a standard unmodified hydraulic braking sy~tem.
Referring to the distribution valve 35, in secondary br3king the servo valves 11-14 are connected to the 1uid return line 34 and the pressure applied to the spools Sl drops. The force of springs 54 is sufficient to overcome any residual pressure and force the spools Sl outwards towards the : servo valves ll-l~ to 6eal~ offi fluid. passages 50 from the : ~ chambers 46-4g and:-~he ports 37 40 which communicate with the ~master cylinder 45 are.uncovered.
'~ Thus,.as thè:~foot.pedal lS is depre~sed brake 1u.id is :forcedtalong the~::fluid:linas S8, 59 ~rom the master c~linder 45, into chamb~rs 46-49 and out o ports 41-44 to ~he brake .mechanism via:the brake line~ 56. ..~
, Since ports 37, ~0 are conneoted~to the fluid line 58 ~and ports 38, 39 are.connected to line ~9 equal pressures are :
, :. . , , . ~ . ~, .,: . . :. ~ . .: . . .
WO90~12718 2 ~ ~ 3 % % 3 PCT/GBgo/00641 . . 1 transferred across each a~le pair of brakes, Loss of system pressure below a certai.n limit will also allow the springs 54 to recover and return to their original state a~d thus has the same effect as if the isolating valve 31 had been de-energised.
Ov~rrid~ Brakinq In the e~ent o~ an undetected failure in the feel system the override mechanism comes into operation. If ~o braking occurs when the dri~er depresses pedal 15 through distance A, he will use a panic force and the pedal will mo~e through distance B. The length of the feel actuator cylinder 18 is such that ~hen the brake pedal 15 has reached the end of travel distance A, the piston head 17a reaches the end of the cylinder 18. Further movement of the pedal 15, i.e. through travel d1stance B on applicaton of a panic force, will cause the piston head 17a to bear on the end face 80 of the cylinder 18, which is attached to the manifold b}ock 75 and thus causes the manifo:ld block 75 to move against and overcome the pre-load o~
riDg 74 so that the whole manifold block 75 mo~es (~o the : positio~ shown as Figure 2). As the maniold block 75 moves toward the support 7~ cylinder 77 mo~es into contact with shaft 76. Further movement of the block 75 caused the shaft 76 to move the piston 66, which acti~ates the brake booster ~Sa and master cyl inder 45 to operate the brakes. ~:
The system is tbus~ery vers tile, self-monitoring, fail-sae and may pertorm to a variety of control laws, such as anti-.
. .
WO 90/12718 ` ~ . ~; PC~/GB90/00643 2~ 33223 lock nraking, variable Dalance, deceleration demand and brakeperformance feed back to pedal.
Although the system described above operates primari ly in dependence upon the load applied to the brake pedal, with appropriate modifications to the system it may be made responsive to the position or movement of the brake pedal or any other parameter measurable in the system.
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Claims (18)
1. A vehicle braking system comprising a braking element operable by a driver; control signal generating means responsive to operation of the braking element; means braking at least one vehicle wheel in response to control signals generated by the control signal generating means; and means for activating an override system to enable direct control of the braking means by operation of the braking element independently of said control signals.
2. A system as claimed in Claim 1, in which said means for activating said override system is a manual switch.
3. A system as claimed in Claim 1 or Claim 2, in which said means for activating said override system operates automatically on detection of a system failure.
4. A system as claimed in any preceding claim, including means for activating said overrride system on application of a force to the braking element greater than a predetermined force.
5. A system as claimed in any preceding claim, in which the means for activating said override system comprises a solenoid valve and a power supply thereto, said override system being activated by de-energisation of the solenoid valve.
6. A system as claimed in Claim 5, in which the solenoid valve is de-energised on failure of the power supply thereto.
7. A system as claimed in Claim 5 or Claim 6, in which the solenoid valve is de-energised by a control signal from said control signal generating means.
8. A system as claimed in any preceding claim, in which said override system comprises means for transmitting a force applied to the braking element to operate the braking means.
9. A system as claimed in Claim 8, in which the transmitting means comprises a hydraulic piston and cylinder arrangement.
10. A system as claimed in Claim 9, in which the braking element moves said piston of said arrangement by hydraulic means.
11. A system as claimed in Claim 9, in which the braking element moves said piston of said arrangment by mechanical means.
12. A system as claimed in Claim 11, in which said mechanical means comprises a moveable rod arranged such that operation of the braking element with a force greater than a predetermined force moves said rod which in turn moves said piston.
13. A system as claimed in Claim 12, including spring means biassing said rod to provide said predetermined force.
14. A system as claimed in any preceding claim, in which the braking element is a foot pedal.
15. A system as claimed in any preceding claim, including means to make the braking means unresponsive to said control signals.
16. A system as claimed in claim 15, in which the means for making the braking means unresiponsive comprises at least one valve the state of which is changeable by the application of pressure thereto.
17. A vehicle braking system substantially as hereinbefore described with reference to the accompanying drawings.
18. A vehicle having a braking system as claimed in any one of Claims 1 to 17.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8909472.6 | 1989-04-26 | ||
| GB898909472A GB8909472D0 (en) | 1989-04-26 | 1989-04-26 | Vehicle braking system |
| GB8910275.0 | 1989-05-04 | ||
| GB898910275A GB8910275D0 (en) | 1989-05-04 | 1989-05-04 | Vehicle braking system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2053223A1 true CA2053223A1 (en) | 1990-10-27 |
Family
ID=26295272
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2053224 Abandoned CA2053224A1 (en) | 1989-04-26 | 1990-04-26 | Vehicle braking systems |
| CA 2053223 Abandoned CA2053223A1 (en) | 1989-04-26 | 1990-04-26 | Vehicle braking systems |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2053224 Abandoned CA2053224A1 (en) | 1989-04-26 | 1990-04-26 | Vehicle braking systems |
Country Status (4)
| Country | Link |
|---|---|
| EP (2) | EP0469052A1 (en) |
| JP (2) | JPH04504697A (en) |
| CA (2) | CA2053224A1 (en) |
| WO (2) | WO1990012718A1 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2762160B2 (en) * | 1990-08-10 | 1998-06-04 | 本田技研工業株式会社 | Hydraulic braking control system for vehicles |
| JP2762161B2 (en) * | 1990-08-10 | 1998-06-04 | 本田技研工業株式会社 | Hydraulic braking control system for vehicles |
| GB9420957D0 (en) * | 1994-10-18 | 1994-12-07 | Lucas Ind Plc | Improvements in pedal assemblies for vehicle braking systems |
| DE29921027U1 (en) † | 1999-11-30 | 2001-06-28 | AL-KO Kober AG, 89359 Kötz | Simulator for a non-hydraulic actuation system |
| JP2013174767A (en) | 2012-02-27 | 2013-09-05 | Sony Corp | Lens barrel and imaging apparatus |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2932620A1 (en) * | 1979-08-11 | 1981-02-26 | Bosch Gmbh Robert | HYDRAULIC FORCE BRAKE SYSTEM FOR A TRAIN VEHICLE WITH TRAILER |
| DE3027747A1 (en) * | 1980-07-22 | 1982-02-18 | Alfred Teves Gmbh, 6000 Frankfurt | CONTROL SYSTEM FOR A VEHICLE BRAKE SYSTEM WITH FLOW AND FRICTION BRAKE |
| DE3342552A1 (en) * | 1983-11-25 | 1985-06-05 | Volkswagenwerk Ag, 3180 Wolfsburg | Hydraulic brake system for motor vehicles provided with a servo device |
| DE3410006A1 (en) * | 1984-03-19 | 1985-09-19 | Alfred Teves Gmbh, 6000 Frankfurt | METHOD FOR CONTROLLING A BRAKE SYSTEM FOR MOTOR VEHICLES, AND DEVICE FOR IMPLEMENTING THE METHOD |
| DE3626751A1 (en) * | 1986-03-22 | 1987-09-24 | Bosch Gmbh Robert | Electro-hydraulic brake system |
-
1990
- 1990-04-26 WO PCT/GB1990/000641 patent/WO1990012718A1/en not_active Application Discontinuation
- 1990-04-26 EP EP19900907210 patent/EP0469052A1/en not_active Withdrawn
- 1990-04-26 JP JP2506660A patent/JPH04504697A/en active Pending
- 1990-04-26 EP EP19900907240 patent/EP0469056A1/en not_active Withdrawn
- 1990-04-26 WO PCT/GB1990/000640 patent/WO1990012717A1/en not_active Application Discontinuation
- 1990-04-26 CA CA 2053224 patent/CA2053224A1/en not_active Abandoned
- 1990-04-26 CA CA 2053223 patent/CA2053223A1/en not_active Abandoned
- 1990-04-26 JP JP2506661A patent/JPH04504698A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| CA2053224A1 (en) | 1990-10-27 |
| JPH04504697A (en) | 1992-08-20 |
| EP0469056A1 (en) | 1992-02-05 |
| WO1990012717A1 (en) | 1990-11-01 |
| JPH04504698A (en) | 1992-08-20 |
| EP0469052A1 (en) | 1992-02-05 |
| WO1990012718A1 (en) | 1990-11-01 |
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Legal Events
| Date | Code | Title | Description |
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| FZDE | Dead |